Such sealing systems are suitable for devices, such as liquid cutting heads, high pressure valves, swivel joints, pumps or the like, which work with a medium at a pressure of, in particular, several 1000 bar. A typical area of application are devices for cutting objects with a jet of water provided with high pressure.
The moveable components in such devices, such as for example the valve needle that can be moved to and fro in a cutting head or in a high pressure valve or the respectively rotating shaft pipe in swivel joints, are generally sealed with plastic seals which should have the most leak-free possible sealing effect as well as a small amount of friction and a long lifespan. One attempts here to minimize the extrusion of the relatively soft sealing elements into the sealing gap with appropriate geometries.
In the previously known sealing systems of this type, either glands or sealing elements with O rings are used. In the first case, sealing elements made of plastic, often with a different hardness, are pre-tensioned between two support rings. They offer the advantage of leak-free sealing of the component, but have the disadvantage that even a small amount of wear may result in the system leaking. Therefore, the sealing element must often be re-tensioned, the pre-tensioning generating high friction forces which increase wear and have a negative impact upon the operability of the device.
When using sealing elements with O rings, a soft seal made of plastic is pre-tensioned with an O-ring. The latter serves as an outer seal, the extrusion being restricted with the aid of the support disc on the atmosphere side, while the liquid pressure undertakes the tensioning of the sealing element. With such sealing systems it is advantageous that the seal adjusts itself to a certain degree when it is worn. Moreover, the pre-tensioning of the sealing element is pressure-dependent. However, it is a disadvantage that leak-free sealing is not guaranteed, in particular at high pressures.